The invention relates to a jointed support structure in accordance with the preamble of claim 1.
Such a jointed support structure, also known as an arm system, is used, for example, when surgical operation areas have to be kept free for or accessible to the surgeon for a longer period. The surgical assistants are relieved in this way and can carry out other work. Such jointed support structures are used to special advantage with operations on hip joints, the abdomen, thorax, mamma and femur. They can also serve as holders in the endoscopy field. The jointed support structure is generally fastened to an operating table rail via a fastening rod and a fastening vice. After a suitable longitudinal displacement and/or horizontal adjustment, surgical aids such as valves or holders are fastened in the mounting provided at the other end of the jointed support structure, preferably as a screw clamp apparatus, and fixed in place via the movement generating device by tightening the central joint. Such jointed support structures can be used as holders in the anaesthetic or intensive care fields or in the minimum invasive field.
In a jointed support structure known from German patent DE 27 17 828, the transmission mechanism is formed by a ball arranged in a wedge-shaped recess which converts an axially applied clamping force into a displacement of the push rod. It is disadvantageous with this known jointed support structure that a substantial amount of force is required on the sides of the movement generating device for the clamping force generated in the clamping jaw element. Furthermore, when the torque is reduced to release the clamping jaw, self-locking can occur so that the release of the clamping is not reliably ensured. Finally, the path reserve of the transmission mechanism of the known jointed support structure is relatively low. A further embodiment operates with a spring plate centrally subject to the pressure of the movement generating device and exerting pressure by its ends on the push rod or the housing of the actuating block. The disadvantage here is that substantial forces are required to exert pressure on the push rod, in particular with an increasing deflection of the spring plate.
A jointed support structure which operates with only one toggle lever has also become known (Swiss patent CH 678 097) which has the disadvantage that the reaction force exerted on a conical nut by the toggle lever results in substantial friction forces between the collet and the surrounding housing, which allows self-locking on the one hand and makes the actuation of the jointed support structure more difficult on the other.
It is the object of the invention to provide a jointed support structure of the kind first mentioned in which
a specific clamping force can be achieved in the clamping jaw element with a reduced expenditure of force at the actuating block;
a self-locking of the transmission mechanism is not to be expected when the actuating force falls off; and
a larger path reserve is available.
The features of the characterising part of claim 1 are provided to satisfy this object.
The path generating device and the toggle lever mechanism are to be made and arranged in such a way that when the largest path is set with the path generating device, the toggle lever is just not yet fully extended so that when the actuating force falls off, a reliable relaxation, i.e. the movement of the toggle lever mechanism into a position with a greater angle, i.e. an unclamping free of self-locking, is ensured.
Moreover, a greater path reserve is also made available due to the toggle lever mechanism, whereby any changes in length of the individual components due to material fatigue and the resulted dreaded loss in clamping power is compensated and/or countered. In this way, overhauls or repairs of the jointed support structure due to a substantial reduction in or loss of the clamping force are avoided.
A clamping force approximately ⅔ higher than the state of the art can be achieved on the basis of the invention with a lower tightening torque or release torque for the same construction and size. In this way, the scope of application and use of the jointed support structure, which is particularly in the field of medical technology, is substantially expanded.
The embodiment of claim 2 has the advantage that the toggle lever system only acts on a single push rod and that a clear relation exists between the movement generating device and the clamping procedure.
The embodiments in accordance with claims 3 and 4 are of particular advantage as, in this way, a particularly stable toggle lever mechanism is achieved which can be manufactured and assembled economically and which can be ideally accommodated in a space-spacing manner in the actuating block, which preferably has a circular horizontal cross section.
Expedient practical developments of the invention can be found in the claims 5 to 12.
The embodiment of claim 13 is particularly advantageous as, in this way, two clamping jaw elements are provided which are connected to one another by the tubular connection elements and the actuating block with one of the clamping jaw elements, for example, being fastened in a suitable manner to the operating table while the other end carries the required medical instruments and/or apparatus.
The two housings can contact one another frictionally and are pressed more or less against one another when the movement generating device is actuated. A respective embodiment is defined in claim 14.
The further developments in accordance with claims 15 to 18 are, however, particularly advantageous because, in this way, the friction between the two housings clamped relative to one another can be increased in a desirable manner. As the reduction in force achieved by the toggle lever arrangement in accordance with the invention also reduces the clamping force between the two housings contacting one another, it is expedient to increase the friction forces between the two housings by the respective measures.
The sliding insert can furthermore prevent metal from rubbing on metal, whereby seizing could occur. The sliding insert can be made, for example, of a suitable plastic material in order, in connection with its special dual tapering shape, to avoid seizing on a relative rotation of the two housings, on the one hand, but also to make available the required friction force, on the other hand, so that after the stressing of the two push rods a relative rotation of the two housings is reliably avoided.
A further development is characterised by claim 19.
The preferred embodiment of the connection element as a tube can be seen from claim 20.
The embodiment in accordance with claim 21 is useful to counter a relative rotation between the pressure plate, housing and toggle levers. Two advantageous embodiments for the rotational security can be seen from claim 22.
A particularly good, low-friction force transmission between the toggle lever mechanism and the push rod is achieved by the measure in accordance with claim 23.
An optimum length adaptation of the push rods to a particular problem can be achieved easily in accordance with claim 24. In addition, various tube connection elements of different length are to be made available. An appropriate arrangement and design of the clamping jaw elements can be seen from claim 25.